A man who assaulted former District 1 City Councilman Harry Mathis at his University City home abruptly pleaded guilty Monday to all charges, including home-invasion robbery.

Harvey Henry Duson, 45, faces a maximum sentence of 250 years to life in prison and a minimum sentence of 27 years, said Deputy District Attorney Martin Doyle.

Duson pleaded guilty on the first day of his trial to setting Mathis’ home on fire to cover up the residential burglary during the Jan. 11 incident. He also pleaded guilty to kidnapping for robbery, three counts of false imprisonment and three robberies.

Mathis, who is the chairman of the San Diego Metropolitan Transit Board, testified he was attacked in his garage after he arrived home from Mayor Jerry Sanders’ State of the City address. He was taken to the hospital after he was beaten on the head.

Duson, who was in Mathis’ garage at 9 p.m., attacked Mathis after he got out of his car. Mathis, who had a concealed handgun for protection, fired two shots, but missed hitting Duson. He was struck on the head with a gun for which he had a permit.

Mathis testified he was assaulted the day before his 79th birthday, but it was “the best birthday I ever had (because) I lived to see it.”

The false imprisonment counts involve holding Harry and Mary Mathis and a neighbor against their wills. The robberies include a holdup of a Sprint store on Rosecrans Street on Nov. 9.

A second man who allegedly accompanied Duson in the crime has not been arrested, and the “investigation is ongoing” as to who he was, said Doyle. Duson left his car on Interstate 8 and was later arrested in Arizona after a collision with another motorist.

Sentencing was set for Dec. 12 by San Diego Superior Court Eugenia Eyherabide. Duson remains in custody on $1 million bail.